Digitization of data is advanced rapidly in the technical field of broadcasting. This is based on, for example, the fact that digital data can use a band more efficiently and can realize higher image quality and higher sound quality than analog data and the fact that the digital data has higher affinity with data except video and sound data than analog data.
When broadcast contents are digital data, since it is possible to carry data for four channels with one channel and to transmit data for a high definition television without change, sophistication and diversification of services are derived. For example, various kinds of system information such as an EPG (Electric Program Guide) is sent together with video information and voice information, whereby it is possible to improve services for users (viewers) (the EPG includes functions such as reservation for recording in a VTR in addition to provision of information such as a broadcast schedule and a program name of a broadcast program).
In addition, since broadcast data of a digital format has high affinity with information apparatuses except a television such as a general purpose computer system, it is expected that broadcasting and communication are fused by the digital broadcasting. For example, a tuner card for digital satellite data broadcasting is attached to a general purpose computer system, received EPG data is analyzed in a computer, and an electronic program table is window-displayed on a computer display, whereby it is possible to realize switching of programs, recording reservation, and the like according to an operation by a mouse cursor. It is needless to mention that it is also possible to digital-recording digital broadcast data in a built-in hard disk of the computer directly. In addition, it is possible to develop a two-way service according to an upper link between a receiving client and a broadcasting station using a computer network.
In addition, recently, a server type broadcast system, which uses a receiver (a television or a video recording and reproduction apparatus) mounted with a large capacity storage such as a hard disk device to receive broadcast contents and reproduce the broadcast contents after temporarily storing the broadcast contents in the receiver, has been widely used.
The server type broadcast system makes it possible to perform, in addition to viewing on a real time basis such as normal television reception, deliver videos and sounds in advance to allow viewing from a designated time and perform scene retrieval and digest viewing using information or the like to be delivered simultaneously.
Incidentally, since broadcast contents are works, proper protection of the broadcast contents from copying without permission and illegal use under the copyright law is essential for development of content production and delivery businesses as well as assurance of benefit for users in that the users enjoy better contents.
However, since it is extremely easy to copy and tamper data and contents of a digital format, the data and the contents are exposed to danger of copyright infringement without protection.
At present, in a digital broadcast system for performing real-time viewing, descriptive information concerning control for digital copy and content usage is inserted into contents, whereby control is carried out on a receiver side such that the contents are used legally in accordance with these pieces of descriptive information.
However, at present, there is no system for sending copyright information for contents in the server type digital broadcasting. In other words, in the server type digital broadcasting, it is also necessary to establish a system that makes it possible to protect broadcast contents stored in a receiver in accordance with the sent copyright information.